Active region

In solar physics and observation, an active region is a temporary feature in the Sun's atmosphere characterized by a strong and complex magnetic field.

They are often associated with sunspots and are commonly the source of violent eruptions such as coronal mass ejections and solar flares.

[2][3][4][5][6] Newly observed active regions on the solar disk are assigned 4-digit region numbers by the Space Weather Prediction Center (SWPC) on the day following the initial observation.

It was first introduced in 1919 by George Ellery Hale and coworkers working at the Mount Wilson Observatory.

Without convection transporting energy from the Sun's interior to the photosphere, surface temperature decreases along with the intensity of emitted black body radiation.